BP report points to chilling sequence of events on Deepwater Horizon 09 September 2010

Halliburton, Transocean and others should shoulder some of the responsibility, alongside BP, for the Deepater Horizon explosion and fire that killed 11 and caused widespread pollution in the Gulf of Mexico earlier this year.

That's one of the key findings of a report – described by rig owner Transocean as self-serving – released yesterday by BP. The other is that no single factor caused the Macondo well tragedy. Rather, a sequence of failures involving these parties and their engineering work and people, were to blame.

In the report – based on a four-month investigation led by Mark Bly, BP's head of safety and operations, and conducted by a team of 50 technical and other specialists drawn from inside BP and elsewhere – BP states that the accident arose from "a complex and interlinked series of mechanical failures, human judgments, engineering design, operational implementation and team interfaces."

BP's report cites the critical failures as starting with the cement and shoe track barriers – and in particular the cement slurry that was used by Halliburton – at the bottom of the Macondo well, which, it says, failed to contain explosive hydrocarbons within the reservoir (as they were designed to do), and so allowed gas and liquids to flow up the production casing.

It then draws attention to the negative pressure test, the results of which were incorrectly accepted by BP and Transocean, although well integrity had not, at that stage, been established.

As for the sequence of events, BP points to its findings that over a 40-minute period, the Transocean rig crew failed to recognise or act on the influx of hydrocarbons into the well, "until the hydrocarbons were in the riser and rapidly flowing up to the surface".

Then, after the well-flow reached the rig, it was routed to a mud-gas separator, causing gas to be vented directly onto the rig, rather than being diverted overboard – with disastrous results. The flow of gas into the engine rooms, through the ventilation system, created a potential for ignition – which the rig's fire and gas system failed to prevent.

Finally BP insists that, after explosion and fire had disabled its controls, the rig's blow-out preventer on the sea-bed should have immediately have sealed the well automatically. However, it too failed to operate, "probably because critical components were not working".

Commenting on the report, BP's outgoing chief executive Tony Hayward said: "To put it simply, there was a bad cement job and a failure of the shoe track barrier at the bottom of the well, which let hydrocarbons from the reservoir into the production casing. The negative pressure test was accepted when it should not have been; there were failures in well control procedures and in the blow-out preventer; and the rig's fire and gas system did not prevent ignition."

Critically for BP, he says that, based on the report, "it would appear unlikely that the well design contributed to the incident, as the investigation found that the hydrocarbons flowed up the production casing through the bottom of the well".

Setting aside, the obvious scope for cynicism, BP's incoming chief executive Bob Dudley said: "We have said from the beginning that the explosion on the Deepwater Horizon was a shared responsibility among many entities. This report makes that conclusion even clearer, presenting a detailed analysis of the facts and recommendations for improvement, both for BP and the other parties. We have accepted all the recommendations and are examining how best to implement them across our drilling operations worldwide."

And he added: "We are determined to learn the lessons for the future and we will be undertaking a broad-scale review to further improve the safety of our operations. We will invest whatever it takes to achieve that. It will be incumbent on everyone at BP to embrace and implement the changes necessary to ensure that a tragedy like this can never happen again."

Since publishing its report, BP has been the buck of searing criticism from environmental groups, politicians in the US and, unsurprisingly, the named parties. They accuse BP variously of attempting to spread responsibility to get the company off the hook and also jumping the gun by not waiting for the results of investigations into the now recovered blowout preventer.

In fairness, BP says it accepts that "additional relevant information may be forthcoming, for example, when Halliburton's samples of the cement used in the well are released for testing and when the rig's blow-out preventer is fully examined now that it has been recovered from the sea-bed".

BP also points to additional information due to come from the multiple ongoing US government investigations.

In the meantime, BP's investigation proposes 25 recommendations, mostly directed at strengthening assurance on blow-out preventers, well control, pressure-testing for well integrity, emergency systems, cement testing, rig audit and verification, but also personnel competence.

Others throughout the oil and gas industry, but also far more generally across the high risk plant sectors, will be studying the report in detail for lessons.

Brian Tinham

Related Companies
BP plc
Halliburton Ltd
Transocean North Sea Ltd

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